Simultaneous Enhancement of Interfacial Stability and Kinetics of Single-Crystal LiNi0.6Mn0.2Co0.2O2 through Optimized Surface Coating and Doping

Abstract

Balancing interfacial stability and Li⁺ transfer kinetics through surface engineering is a key challenge in developing high-performance battery materials. Although conformal coating enabled by atomic layer deposition (ALD) has shown great promise in controlling impedance increase upon cycling by minimizing side reactions at the electrode–electrolyte interface, the coating layer itself usually exhibits poor Li⁺ conductivity and impedes surface charge transfer. In this work, we have shown that by carefully controlling postannealing temperature of an ultrathin ZrO₂ film prepared by ALD, Zr⁴⁺ surface doping could be achieved for Ni-rich layered oxides to accelerate the charge transfer yet provide sufficient protection. Using single-crystal LiNi_0.6Mn_0.2Co_0.2O₂ as a model material, we have shown that surface Zr⁴⁺ doping combined with ZrO₂ coating can enhance both the cycle performance and rate capability during high-voltage operation. Surface doping via controllable postannealing of ALD surface coating layer reveals an attractive path toward developing stable and Li⁺-conductive interfaces for single-crystal battery materials.